Choosing a starting curve for linearization


#41

Keith,
I made the scaled tif back in July after I got back from Taos. I scaled it so it would fit on 7-3/8 x 11 Arches platine, which is the size you get if you quarter an 11 x 15 sheet. I printed a negative with the scaled tif plus the master quad, and I have used that same July negative whenever I print a spyder+master target.

If I open my scaled tif in PS,I get a warning that there is no embedded profile. ExifTool says the ColorSpace is “Uncalibrated.” But you’re right – there’s no way to know it’s Gray Gamma 2.2. Whether or not there is a problem, I’m never going to use that tif again!

I was going to make a new spyder + master negative this evening using the original tif from PiezoDN-Windows. However I needed an ink change, which led to a full printer maintenance after “PK” (which is matte black on my printer) refused to give a good nozzle check, even after multiple head cleaning (all the other channels are fine). I used the dummy cartridge with the syringe twice to inject and withdraw PiezoFlush and did numerous head cleanings. The gaps in “PK” vary from just a few to nearly blank. They don’t progressively get better, as you would expect. For example, I may have a dozen gaps. After a head cleaning, the PK pattern is completely blank! I wonder if there is something stuck INSIDE the cartridge that’s blocking the cartridge outlet. I may have picked up a piece of debris when I filled the PK cart from near the bottom of the matte black bottle.


#42

I know it’s a long shot, but I just wanted to put it out there - just in case.

FWIW - your DN profiles don’t use the MK ink that is in your PK position. They use PK ink which is in the Y position. Therefore, you really could proceed even though the PK position has gaps.

Signing off now …


#43

Keith,
That’s a great idea. I was pretty sure PiezoDN didn’t use matte black. Yet it disappears. It helps me track the cost of head cleanings and nozzle checks.


#44

Walker,
Your Cyano-Master-2.quad uses these inks:
walker%20quad%20inks

It doesn’t use yellow. It uses both blacks.

The quads in R2000-P2-PiezoDN (which I’m using for the P400) use these inks:
image

I haven’t tried printing with Cyano-Master-2.


#45

John - I might be going blind but those ink keys look the same to me. Just to be sure, are you using the ink placements for P400/R2000 P2 as shown on this page?https://piezography.com/epson_p400_installation

Y = PK
M = Shade 6
MK = Shade 2
R = Shade 3
OR = Shade 4
PK = MK
GL = GL
C = Shade 5

A misplaced ink might be the cause of the unexpected linearization result, though I think there would also be some weird reversals.


#46

Keith,
Sorry, I posted the the same image twice. Here are the P400 inks:

P400%20inks


#47

Oxidation occurs after a cyanotype print is made, causing it to darken. I use H2O2 at the end of development to accelerate oxidation. But but does further oxidation occur even after the H2O2? If so, variation in the age of each print at the time of measurement will affect linearization. If I measure a print that has not oxidized sufficiently, QTR-Linearize-Quad will want to darken it by decreasing density of the negative. If, in the next iteration, I measure a fully oxidized print, QTR-Linearize-Quad will want to lighten it by adding density to the negative. This adding (or subtracting) of density would be (as Keith writes) “throughout the scale.”